The stars have ordained to Zodac, the rider of the solar winds, that he must save the life of Skeletor by destroying He-Man. So with that in mind, he appears to the royal court in his sun chariot to appeal to the hero (whom he knows is Adam) to either come to him or be responsible for the destruction of Eternia by way of Zodac's cosmic power. Adam exits from the palace with Cringer by his side to hear the cry of the falcon, whereupon he enters the Cave of Power and transforms into He-Man. There, the Sorceress tells him of Skeletor's search for the other half of the Power Sword (as He-Man does not have it...yet). Meanwhile, Superman is flying near Metropolis harbors when a giant sea creature attacks him. This turns out to be because of a warp at the bottom of both Earth's and Eternia's ocean. After disposing of the monster, Supes follows three glowing spheres to the bottom of the ocean, only to be caught in a vortex and emerge, once again, in Eternia. He-Man has begun to battle with Zodac, who easily matches him. Skeletor recovers the second half of the Power Sword (from its secret location on Earth) and is about to join the two when Superman flies over and grabs both. Skeletor attacks Supes with magic, and Superman gets rid of the two halves by throwing one to He-Man and one at Skeletor. He-Man throws his half into Skeletor's chest as Skeletor electrocutes He-Man and both die. But Skeletor's power enters into He-Man and he rises again, whereupon Zodac tells him that he has cheated his fate.
(An interesting story of how He-Man got his half.)